Liquid-liquid solvent extraction is used in hydrometallurgical processes for the recovery and refining of valuable minerals, for example, rare earth and precious metals, copper, vanadium, nickel, cobalt and the extraction of uranium from wet process phosphoric acid. In most of these liquid-liquid solvent extraction processes, a highly ionic aqueous solution, which is highly acidic or basic and carries valuable metals, is contacted with an organic solution containing a liquid-liquid solvent extraction agent dissolved in a suitable inert diluent such as kerosene. Contact between the two liquid phases effects a metal transfer from the highly ionic aqueous phase into the immiscible organic phase and results in a raffinate essentially barren of the valuable metal. However, this raffinate does contain entrained and dissolved liquid-liquid solvent extraction agents and inert organic diluents as a result of the liquid-liquid solvent extraction process. This results in a significant loss of from a few parts per million to several hundred parts per million of the solvent extraction agent and diluent. Such a loss occurs at a significant cost to the operation of a hydrometallurgical process. Further, because the raffinate is often recycled back into the process, the presence of solvent extraction agent and organic diluent (also referred to as uranium process organics) in the highly ionic aqueous raffinate is sometimes incompatible with ensuing operations. For example, the contaminated ionic aqueous raffinate may adversely affect further chemical processing of the raffinate or it can be detrimental to plant equipment by causing a deterioration of rubber elements in the equipment.
The prior art has taught the use of the polymers of the present disclosure for the removal or concentration of organic substances. U.S. Pat. No. 2,974,178 to Hwa, et al teaches the use of a polyethylenically unsaturated polymer containing vinyl or vinylidene groups to concentrate a component of a homogeneous liquid mixture of non-ionogenic character. U.S. Pat. No. 3,531,463 to Gustafson teaches the use of similar polymers for separating water-soluble substances having hydrophobic and hydrophilic portions in their molecules from an aqueous medium. Neither one of these patents recognizes the use of such polymers for the recovery of organic substances from highly ionic hydrometallurgical raffinates. Hwa, et al specifically teaches against the use of such a polymer in an ionic solvent.